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Bridging the gap: development of a methodology for retrieving and harmonising body mass index (BMI) from population-level linked electronic health records

Michael Childs, Sarah Aldridge, Helen Daniels Orcid Logo, Gareth Ivor Davies, Victoria Best, Hoda Abbasizanjani Orcid Logo, Ronan Lyons, Ashley Akbari Orcid Logo, Fatemeh Torabi Orcid Logo

BMJ Open, Volume: 15, Issue: 10, Start page: e103724

Swansea University Authors: Michael Childs, Sarah Aldridge, Helen Daniels Orcid Logo, Victoria Best, Hoda Abbasizanjani Orcid Logo, Ronan Lyons, Ashley Akbari Orcid Logo, Fatemeh Torabi Orcid Logo

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Abstract

Objective This study aims to develop a methodology to retrieve, harmonise and evaluate the completeness of national body mass index (BMI) data from linked electronic health record (EHR) sources to build a longitudinal research-ready data asset (RRDA).Design A longitudinal study of BMI records spanni...

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Published in: BMJ Open
ISSN: 2044-6055 2044-6055
Published: BMJ 2025
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa70456
Abstract: Objective This study aims to develop a methodology to retrieve, harmonise and evaluate the completeness of national body mass index (BMI) data from linked electronic health record (EHR) sources to build a longitudinal research-ready data asset (RRDA).Design A longitudinal study of BMI records spanning 23 years (1 January 2000 to 31 December 2022) from four data sources.Setting The national BMI RRDA is created within the Secure Anonymised Information Linkage (Databank), encompassing the entire population of Wales, UK.Procedure and participants We built a methodology that provides a reproducible framework for extracting and harmonising BMI data from four major linked EHRs across two age groups: children and young people (CYP; 2–18 years old) and adults (19 years and older). The methodology is adaptable across different trusted research environments. We evaluated the completeness and retention of records over 1-, 5- and 23-year periods by calculating the proportion of missing data relative to each year’s population.Results We retrieved 53.4 million records for 3.2 million individuals across Wales from 1st January 2000 to 31 December 2022. Among these, 3% of CYP and 34% of adults had repeat BMI measurements recorded over periods ranging from 5 to 23 years. Throughout the entire population of Wales during this period, 49% of CYP and 26% of adults had at least one BMI reading recorded, resulting in a missingness rate of 51% for CYP and 74% for adults. Preserving BMI information by retaining the most recently recorded BMI over 1-, 5- and 23-year intervals from 2022 showed coverage rates of 10%, 33% and 68%, respectively, for CYP, and 25%, 51% and 73%, respectively, for adults.Conclusions Our findings highlight substantial variations in BMI data availability and retention across CYP and adults, as well as time periods within EHR in Wales. Wider adoption of this approach can enhance standardised approaches in using accessible measures like BMI to assess disease risk in population-based studies, strengthening public health initiatives and research efforts.
College: Faculty of Medicine, Health and Life Sciences
Funders: ADR; Economic and Social Research Council - ES/W012227/1; HDR UK Ltd - HDR-9006; Medical Research Council - MR/V028367/1
Issue: 10
Start Page: e103724